1. Field of the Invention
This invention relates generally to flex joints for pressure vessels and more particularly to an airtight, flexible joint for the interfacing of two pressure vessels such as between the Space Station docking tunnel and the Space Shuttle Orbiter's bulkhead adapter.
2. Brief Description of the Prior Art
Prior methods of providing a load-carrying flex joint between pressure vessels include using a flexible bellows along with a separate, adjustable structural linkage system, or a spherical ball-joint type interface with dynamic seals.
The disadvantages of using a bellows or other type of flexible material section is that the parallel structural link must not only hold the loading created by the pressure differential, but it must be designed to adjust for position/angle misalignment, possible even dynamic motion. This requires a system that is most likely very mechanically complex, especially if it is to be unbiased in its orientation, or if it is to also act as a load-limiter. A spherical ball-joint requires a dynamic seal, and it does not allow for any misalignment or adjustments other than angular. To adjust laterally, two ball-joints and a telescoping segment must be used in series, a configuration which requires extra space due to its length.
Rogemont U.S. Pat. No. 4,624,465 discloses a seal joint designed to be used in a slot or groove. The joint has an inflatable internal volume of pressurized fluid and an external seal surface. The joint is made to withstand pressure, deformation, and extension. The joint may be used for nuclear, aerospace, electronic, and medical areas.
Anderson U.S. Pat. No. 1,859,065 discloses a joint for pipes or vessels which contain pressurized fluid comprising a liquid or a gas. The joint is used to connect one of the members to an opposite member, wherein one of the members which is slightly flexible at its end is acted upon by an internal pressure in such a way as to have a fluid-tight contact with the opposite member. See col. 1, lines 12-29.
Bechu U.S. Pat. No. 4,819,565 discloses a tubular joint or a sealing joint for connecting two successive members. The joint is a U-shaped membrane filled with pressurized fluid. The joint can withstand all mechanical pulls exerted upon it and has a very high durability.
Fidler et al. U.S. Pat. No. 3,773,338 discloses a flexible seal which connects two members together. The flexible seal has a predetermined range of multi-directional fluctuations while maintaining sealing contact with two members.
The present invention is distinguished over the prior art in general, and these patents in particular by an airtight, flexible joint designed for the interfacing of two pressure vessels such as between the Space Station docking tunnel and the Space Shuttle Orbiter's bulkhead adapter. The joint provides for flexibility while still retaining a structural link between the two vessels required due to the loading created by the internal/external pressure differential. The joint design provides for limiting the axial load carried across the joint to a specific value, a function required in the Orbiter/Station tunnel interface. The flex joint comprises a floating structural segment which is permanently attached to one of the pressure vessels through the use of an inflatable seal. The geometric configuration of the joint causes the tension between the vessels created by the internal gas pressure to compress the inflatable seal. The inflation pressure of the seal is kept at a value above the internal/external pressure differential of the vessels in order to maintain a controlled distance between the floating segment and pressure vessel. The inflatable seal consists of either a hollow torus-shaped flexible bladder or two rolling convoluted diaphragm seals which may be reinforced by a system of straps or fabric anchored to the hard structures. The joint acts as a flexible link to allow both angular motion and lateral displacement while it still contains the internal pressure and the holds the axial tension between the vessels.